The invention relates in particular, though not exclusively, to the high volume, continuous production of aluminium products, such as heat exchangers and oil coolers for automotive applications. Typically a tunnel type furnace is employed for brazing together of the aluminium component parts.
Although aluminium is more difficult to braze than many other metals, the lightness of weight and good thermal conductivity of aluminium render it particularly suitable for automotive and similar applications.
In order successfully to braze aluminium it is necessary for the component parts to be de-greased and for a brazing flux to be applied, typically in the form of an aqueous suspension that is then dried prior to the component parts entering the tunnel furnace. Furthermore, in order to avoid renewed oxide formation within the furnace it is necessary to provide an inert gas, typically nitrogen, within the furnace. On exit from the heated brazing zone within the tunnel furnace the brazed product is then force cooled prior to subsequent manufacturing and finishing operations.
An example of a typical and well-proven apparatus is shown diagrammatically in FIG. 1 of the accompanying drawings. It shows in sequence a degreaser unit 1, a fluxer unit 2, a dryer unit 3, a tunnel furnace 4 comprising an entry curtain box, heating zone and atmospheric gas type cooling zone, and a final air cooling unit 5.
Each of the degreaser, fluxer and dryer units comprises a respective conveyor 6 for feeding components into the unit, transportation through the unit and removal from the unit. End rollers 7 of successive neighbouring conveyor belts are provided close together for smooth transfer of components between the units. A conveyor 8 is provided for feeding components into the entry curtain box, for transportation through the successive zones of the tunnel furnace, through the final air cooling unit and for removal from the air cooling unit. The upstream end roller of the conveyor 8 is positioned close to the downstream end of the dryer unit conveyor, again for smooth transfer of components therebetween.